The Severe Thunderstorm Arrival Tool is a resource for municipalities, counties, and SKYWARN storm spotters to plan for possible storm spotter activation on the current calendar day. Other interests can also use the Severe Thunderstorm Arrival Tool to determine the expected time frame for severe thunderstorm potential.

Probability of a tornado within 25 miles of a point:less than 10 percent.
Be aware of where your closest interior shelter is located.

Elevated

Probability of a tornado within 25 miles of a point:Equal to or greater than 10 percent.
Be prepared to move to the closest strong interior shelter if you are in a vulnerable location: outdoors, in a motor vehicle, mobile home, or other vulnerable structure.

Significant

Probability of a tornado within 25 miles of a point:Equal to or greater than 30 percent.
Plan to move to your closest strong interior shelter if you are in a vulnerable location: outdoors, in a motor vehicle, mobile home, or other vulnerable structure.

Extreme

Probability of a tornado within 25 miles of a point:Equal to or greater than 45 percent.
Plan to move to your closest strong interior shelter if you are in a vulnerable location: outdoors, in a motor vehicle, mobile home, or other vulnerable structure.

Risk of sub-severe hail (less than 1")orProbability of severe hail (1" or greater) within 25 miles of a point:less than 15%
Be aware of potential need to move vehicles, people, and animals for protection.

Elevated

Probability of severe hail (1" or greater) within 25 miles of a point: Equal to or greater than 15%
Be prepared to move vehicles, people, and animals for protection.

Significant

Probability of severe hail (1" or greater) within 25 miles of a point:Equal to or greater than 45%
Plan to move vehicles, people, and animals for protection.

Extreme

Probability of severe hail (1" or greater) within 25 miles of a point:Equal to or greater than 60%
Plan to move vehicles, people, and animals for protection.

Risk for sub-severe wind gusts (less than 58 mph) orProbability of severe wind gusts (58 mph or greater) within 25 miles of a point:Less than 15%
Be prepared to secure unsecured property to prevent wind damage.

Elevated

Probability of severe wind gusts (58 mph or greater) within 25 miles of a point:Equal to or greater than 15%
Be prepared to secure unsecured property to prevent wind damage. Prepare to move to an interior shelter.

Significant

Probability of severe wind gusts (58 mph or greater) within 25 miles of a point:Equal to or greater than 45%
Plan to secure unsecured property to prevent wind damage. Plan to move to an interior shelter.

Extreme

Probability of severe wind gusts (58 mph or greater) within 25 miles of a point:Equal to or greater than 60%
Plan to secure unsecured property to prevent wind damage. Plan to move to an interior shelter.

Thunderstorms expected to be isolated to scattered in coverage. Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms.
Be aware for thunderstorms in your area.

Elevated

Thunderstorms expected to be numerous in coverage.Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms.
Be prepared to take immediate shelter from thunderstorms and lightning.

Significant

Widespread thunderstorms are expected.Atmospheric conditions support cloud to ground lightning strikes in and near thunderstorms.
Plan to take immediate shelter from thunderstorms and lightning.

Extreme

Thunderstorms are expected with nearly continuous cloud to ground lightning strikes in and near thunderstorms.
Plan to stop all outdoor activity and move to shelters. Remain in shelters until all danger of wind and lightning has passed.

Risk of localized flash flooding of small streams and low water crossings, and minor flooding of poor drainage or urban areas.
Be aware of flood prone areas and potential to change your driving course if roadways flood.

Elevated

Risk of flash flooding of several low water crossings, roads, and small streams,orMinor River Flooding.
Be prepared to move away from flood prone areas. If you observe flooded roadways, be prepared to change your driving course.

Significant

Risk of flash flooding of numerous roads, low water crossings, and small streams,orModerate river flooding.
Plan to move away from flood prone areas. If you observe flooded roadways, change your driving course or stay off roads completely.

Extreme

Risk of widespread flash flooding of low water crossings, roads, and small streams.orMajor river flooding.
Plan to move away from flood prone areas. If you observe flooded roadways, change your driving course or stay off roads completely.

Open burning is usually safe with proper containers and precautions under low fire danger conditions. Residents should always check on local ordinances that prohibit open burning under any conditions.

Limited

Open burning is usually safe with the proper precautions.
Burning should be done in the early morning and late evening to avoid windier and drier conditions from midday through mid-afternoon. Residents should always check on local ordinances that prohibit open burning under any conditions.

Elevated

Any open burning is discouraged due to increased wind and lower humidity - except by experienced fire personnel. Increasing winds and lower humidity contribute to drying fuels. Fires escape control more easily and containment is difficult for inexperienced fire personnel.Approaching Red Flag conditions.

Significant

Open burning should not be attempted.High winds and extended dry periods lead to extreme burning conditions. Open fires can quickly escape and are very difficult to control, even for experienced fire fighters.
Conditions exceed minimum criteria for a Red Flag Warning in most cases.

Extreme

Very strong winds, well in excess of Red Flag Criteria combined with moderate to low humidity.Fires will spread very quickly with spot fires common. Fire control is extremely difficult due to very strong winds.

These definitions should not be confused with the standard National Fire Danger Rating System (NFDRS) adjectives used by wildland fire personnel. Please visit the Minnesota DNR or Wisconsin DNR pages for your local fire danger rating.

The fire weather category for the Enhanced Hazardous Weather Outlook is based primarily on predicted wind, humidity and temperature, and does not account for fuel moisture from recent precipitation, snow cover and recently melted snow. Appropriate adjustments to the fire environment must be made.

Fire weather hazard categories will normally be more restricted, generally in the "none" or "limited" categories from June 1st to September 30th due to normally predominant green and moist live vegetation. This will be subject to change during unusual severe Spring and/or Summer drought.

Favorable to marginal weather conditions with moderate to high moisture content of grasses and other dry organic material on the ground, indicating that the probability of a fast moving fire is low to a slight potential. Outdoor burning under these conditions can usually be performed with reasonable safety precautions, but should be monitored. Difficulty of fire suppression: Headfire can generally be stopped by road and tracks in low conditions and with water under moderate conditions.

High

Unfavorable weather conditions and low moisture content of grasses and other dry organic material on the ground, indicating that there is a high potential for fire to spread. Outdoor burning should be restricted to early morning or evening hours when wind speeds are usually lower and the relative humidity is higher. Burning is still favorable for well-planned burns by experienced land management personnel. Difficulty of fire suppression: Headfire attack generally successful with water.

Very High

Very poor weather conditions and very low moisture content of grasses and other dry organic material on the ground, indicating that dangerous burning conditions exist. Fires will spread rapidly and show erratic behavior. Outdoor burning is not recommended other than for experienced land management personnel. Difficulty of fire suppression: Direct headfire attack will become increasingly difficult. Spot fires are more likely.

Extreme (GFDI 50-75)

Extreme weather conditions and very low moisture content of grasses and other dry organic material on the ground, indicating that critical burning conditions exist. All fires have the potential to become large and spread quickly and become erratic with extreme fire behavioral characteristics. Difficulty of fire suppression: Direct attack on a headfire will generally fail. Back burn from a secure good line with adequate manpower and equipment. Flanks may become more difficult to control in shifting or erratic winds. Spot fires are likely.

Extreme (GFDI > 75)

Extreme grassland fire weather conditions that are rarely experienced in our area. Very high winds and low humidity with very dry cured grasses. Any fire that starts will spread rapidly and almost impossible to control. Fire suppression: Direct attack will likely fail, especially in heavy fuel loads.

The Grassland Fire Danger Index (GFDI) is a numerical value that indicates the potential for grassland fires to experience extreme fire behavior. The GFDI combines the curing (%), temperature (deg C), relative humidity (%), and the average of the sustained wind and wind gust speed (km/hr).

This index is mainly valid for Iowa. For the latest fire danger ratings in Minnesota or Wisconsin, please visit the Minnesota DNR or Wisconsin DNR web sites.

Very light freezing rain or drizzle with up to a thin glaze, OR Freezing Fog.
Be aware of locally hazardous travel conditions on bridges, overpasses, and untreated or secondary roads.

Elevated

Freezing rain or drizzle with accumulation less than 1/4 inch.
Be prepared to reduce travel speed for hazardous travel conditions especially on bridges, overpasses, untreated and secondary roads.

Significant

Freezing rain with accumulation of 1/4 inch to less than 1 inch.
Plan for hazardous travel conditions. Powelines and trees may be damaged resulting in localized to scattered power outages. Avoid travel if possible and prepare for possible power outages.

Extreme

Freezing rain with accumulation of greater than or equal to 1 inch.
Travel will be dangerous and may be impossible. Powerlines and trees likely damaged resulting in widespread power outages. Avoid travel unless it is an emergency and prepare for extended power outages.

Frost and Freeze Legend

Risk Level

Definition

None

No danger of frost or freeze causing damage to vegetation.

Limited

Patchy frost during the growing season with minor damage to unprotected vegetation.
Be aware that vegetation may need to be protected.

Elevated

Frost expected during the growing season with damage to unprotected vegetation.This may include temperatures less than or equal to 32 degrees F for less than 3 hours.
Be prepared to protect vegetation.

Significant

Freeze expected(less than or equal to 32 degrees F for 3 or more hours) during the growing season with significant damage to unprotected vegetation.
Protect vegetation.

Extreme

Hard freeze (less than or equal to 28 degrees F) during the growing season with catastrophic damage to unprotected vegetation.
Protect vegetation when watches and warnings are issued.

Minimum apparent temperature < -4 deg. F.
Frostbite and hypothermia may occur with prolonged exposure without proper clothing. Be aware to have proper clothing for exposure and limit or eliminate exposure if possible.

Elevated

Minimum apparent temperature < -19 deg. F
Frostbite and hypothermia could occur within 30 minutes without proper clothing. Be prepared to have proper clothing for exposure and limit or eliminate exposure if possible.

The ExperimentalEnhanced Hazardous Weather Outlook is an experimental product that will be posted to this page for evaluation. We encourage your comments or suggestions for improvements using the electronic survey provided. Your feedback will help us determine product utility, if modifications are needed, and whether the product should become part of our operational suite. | Product Description Document

The ExperimentalEnhanced Hazardous Weather Outlook is a decision support service that supports preparedness and response efforts prior to and during hazardous weather. This service provides decision makers with convenient access to potential weather hazard information by graphically depicting the risk of weather hazards out through seven days.